1. Field of the Invention
The present invention relates generally to containers for storing liquids and, more particularly, to a double walled tank and a method of constructing the same.
2. Discussion of the Prior Art
It is known to form a single-walled tank out of polyolefin or other suitable plastic material, for use in storing agricultural and industrial chemicals. These tanks are commonly formed by any of a number of different molding processes, such as rotation molding or the like.
Where these conventional containers are used to store chemicals which are potentially harmful to the environment, federal regulations require the use of an accompanying containment system for ensuring that any chemicals leaking or otherwise released from the tank are prevented from escaping the system. In this manner, it is possible to clean up after leaks and spills and to dispose of waste chemicals in a safe and proper manner.
A number of problems are presented to the use of these conventional tanks and containment systems. For example, a single walled container experiences both mechanical stress due to the outward pressure exerted on the tank by the chemicals contained therein, and chemical attack on the material used to form the container. Because the adverse effects of the chemical attack on the tank material are accelerated when the material is under mechanical stress, the useful life of a single walled container is severely limited.
Also, because the tank is formed with only a single wall, it does not provide full containment of the chemicals stored therein, but must be used in connection with a further containment system. Because conventional containment systems do not allow for the recapture and re-use of contaminated chemicals that leak from the tank, quantities of chemicals must be disposed of after a leak has occurred.
Attempts have been made to form a tank with a double-thickness wall by forming an interior wall within a pre-molded tank in an effort to build up the strength of the tank. However, this technique has proven unsatisfactory because in order to adequately cure the inner wall it is difficult not to over cure the previously formed outer wall.